Facebook employees are learners. That's why the most important trait VP of HR Janelle Gale looks for in job candidates is curiosity.

"We look for learners, people who are acquainted to learning fast, are intellectually curious, and constantly looking to expand their knowledge," she told Business Insider. "They're actively seeking feedback and they're open to it."

And, as with any company, hiring the right people is crucial to helping Facebook maintain its culture.

For Gale, if displaying an interest in learning is the key to getting hired, then coming across as intellectually closed-off is a major red flag.

That applies to everyone — even top experts.

"If you've got literally the smartest person in the room, who is the top expert in whatever they're doing, and they're not opening to learning, that is a huge red flag for us," she said. "We need people who are looking to incorporate new behaviors, new information, and new data, into their repertoire and skills."

Gale said that people who already think they know it all also typically overestimate themselves.

"There's just so much to learn here, no matter if you're an entry level college graduate or if you're top in your field," she said. "Cockiness does not work."

So how does Facebook weed out the know-it-alls? Gale said she'll often ask follow-up questions about projects the individual has worked on, like "What would you have done differently?" or "What did you learn in the process?"

"If someone hesitates for a really long time and can't come up with an answer, or if they spin it so that what they learned actually makes them look good, that tells me that they are closed off to learning," she said.

What she wants from the candidate is a level of vulnerability and reflection, as well as a strong demonstration of intellectual curiosity.

"I want someone to answer that question saying, 'Oh, there's a ton I learned from that' or 'Let me give you the top one, but there's so much more,'" Gale said. "The ability to incorporate new knowledge and information into what you're doing allows us to move faster, because you're learning faster."